Scalable Vector Graphics
is good technology for drawing images on web pages. It's sort of a
forgotten tech; SVG dates back to 1999 but lack of IE support
hamstrung adoption. But it works great in every modern browser,
including IE9, and it's beautiful. A lot of the focus for HTML5 drawing
has been about canvas. But SVG is very
capable and better suited for document presentation.

SVG is a vector graphics format: you write a description
of objects in the drawing as a set of declarations: "red square at
(50,50)", "the word vector rotated 30° and flipped". Then the
browser renders the scene graph. The
underlying XML isn't too verbose and the syntax for transformations and paths and the like is a
shorter text format. SVG is remarkably capable in what it can draw and
browsers do a beautiful job of rendering with anti-aliasing. Given how
rare SVG usage has been it's amazing how good the implementations are.

This blog post contains some simple SVG: if you don't see a wind rose
in the upper right click through to my blog.
Should work in IE9, Firefox 4, and Chrome. (Doesn't work in Safari and
older Firefox because of XML namespace issues unique to my blog). If you
view the source you can see the code for the diagram. It's basically a
bag of <path> elements, each of which draws a wedge and translates
it.

I first understood SVG's value when talking to Mike Bostock about his genius
Javascript visualization libraries Protovis, Polymaps, and D3. SVG is a declarative
document, so it's very easy to manipulate the scene graph via DOM and
Javascript. Mike's libraries have turned that capability into beautifulinteractive
visualizations.

SVG is pretty easy to program. You can write it by hand, but for
building SVG in Javascript I recommend D3: it does for SVG what
jQuery did for DHTML. A key debugging tool is DOM inspection. Browser
developer tools let you easily examine and modify the generated SVG on
live documents. For docs, the resource I keep going back to is the SVG spec; it's remarkably well
written. O'Reilly also publishes a free
online book.